Resistance of sheep to laboratory infestations of the tick, Ixodes ricinus

The development of tick resistance was studied in three one-year-old female Galway cross ewes which received up to three staggered infestations of 100 adult pairs of Ixodes ricinus. Sheep acquired resistance after the first infestation and the ticks showed suppressed feeding and oviposition success. The histology of tick-bite lesions revealed a cellular infiltrate consisting predominantly of neutrophils and this was followed by the infiltration and degranulation of basophils. Mononuclear cells accompanied basophil infiltration and then dominated the cellular infiltrate. Eosinophils infiltrated tick-bite lesions in considerable numbers especially in the tertiary infestation, in which degranulation of mast cells and basophils was also most rapid.     

A computer simulation of the effects of specific environmental factors on the development of the sheep tick Ixodes ricinus L

A previously developed technique for predicting field development rates of the tick, Ixodes ricinus, has been modified and used in an attempt to test interpretations of field data and to gain further insight into the population dynamics of I. ricinus. The results of this study have provided encouraging evidence of the validity of the predictive technique, identified certain areas in the biology of I. ricinus which require further investigation and, in general, supported the suggestion that in Ireland a continuous interchange of ticks between spring and autumn populations occurs. This technique requires further refinement but it appears to have considerable potential for predicting the behaviour of tick populations in different localities and under the influence of different weather conditions.     

A morphological and molecular study of Anaplasma phagocytophilum transmission events at the time of Ixodes ricinus tick bite

Background

Anaplasma phagocytophilum is the causative agent of human granulocytic anaplasmosis (HGA) in humans and tick-borne fever (TBF) in ruminants. The bacterium invades and replicates in phagocytes, especially in polymorphonuclear granulocytes.

Methods

In the present study, skin biopsies and ticks (Ixodes ricinus) were collected from tick feeding lesions on 38 grazing lambs between two and three weeks after access to pastures. The histopathological changes associated with tick bites and A. phagocytophilum infection, were described. In addition the skin biopsies were examined by immunohistochemistry. Furthermore, samples from blood, skin biopsies and ticks were examined by serology, PCR amplification of msp2 (p44), genotyping of rrs (16S rRNA) variants, and compared with the results obtained from histological and immunohistochemical investigations.

Results

Tick bites were associated with chronic and hyperplastic inflammatory skin lesions in this study. A. phagocytophilum present in skin lesions were mainly associated with neutrophils and macrophages. Bacteria were occasionally observed in the Tunica media and Tunica adventitia of small vessels, but were rarely found in association with endothelial cells. PCR and genotyping of organisms present in blood, ticks and skin biopsies suggested a haematogenous and a local spread of organisms at the tick attachment sites.

Conclusions

The present study describes different aspects of A. phagocytophilum infection at the site of tick bite, and indicates that A. phagocytophilum rarely associates with endothelium during the early pathogenesis of infection.     

Efficacy of a collar impregnated with amitraz and pyriproxyfen for prevention of experimental tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs

OBJECTIVE: To compare the efficacy of collars impregnated with 9% amitraz or 9% amitraz and 0.5% pyriproxyfen (PPF) for control of newly established tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs and determine whether egg production by surviving female ticks was decreased. DESIGN: Prospective study. ANIMALS: 72 dogs. PROCEDURE: Dogs were fitted with 1 of 3 test collars impregnated with amitraz, amitraz and PPF, or only excipients (untreated controls). In 3 trials corresponding to each of the 3 tick species, dogs were infested with 150 unfed adult ticks on days 8, 10, 13, and 18. The number of feeding female ticks was recorded on days 10, 13, 18, and 28. Surviving females were weighed and permitted to oviposit under controlled conditions. RESULTS: Collars impregnated with amitraz and PPF decreased tick loads as efficiently as collars containing amitraz alone. Inclusion of PPF into the collar did not significantly decrease the efficacy of amitraz. The few female ticks that survived after feeding on dogs treated with collars containing PPF were unable to oviposit. CONCLUSIONS AND CLINICAL RELEVANCE: Collars impregnated with amitraz were efficient in preventing tick infestations in dogs but did not inhibit oviposition in the few surviving female ticks. Incorporation of PPF into the amitraz-impregnated collar resulted in impairment of the reproductive ability of ticks.     

Geographical distribution and prevalence of tick‐borne encephalitis virus in questing Ixodes ricinus ticks and phylogeographic structure of the Ixodes ricinus vector in Norway

The tick‐borne encephalitis virus (TBEV), a zoonotic flaviviral infection, is endemic in large parts of Norway and Eurasia. Humans are mainly infected with TBEV via bites from infected ticks. In Norway, the main geographical distribution of ticks is along the Norwegian coastline from southeast (~59°N) and up to the southern parts of Nordland County (~65°N). In this study, we collected ticks by flagging along the coast from Østfold County to Nordland County. By whole‐genome sequencing of the mitochondrial genome of Ixodes ricinus, the phylogenetic tree suggests that there is limited phylogeographic structure both in Norway and in Europe. The overall TBEV prevalence is 0.3% for nymphs and 4.3% for adults. The highest estimated TBEV prevalence in adult ticks was detected in Rogaland and Vestfold County, while for nymphs it is highest in Vestfold, Vest‐Agder and Rogaland. The present work is one of the largest studies on distribution and prevalence of TBEV in ticks in Scandinavia, showing that the virus is wider distributed in Norway than previously anticipated.     

Compatibility of the fungus Metarhizium anisopliae and deltamethrin to control a resistant strain of Boophilus microplus tick

The tick Boophilus microplus causes economic impact to cattle producers and has a great capacity to develop resistance to chemical acaricides. It is very important the development of new techniques to complement the control of this parasitosis. Biological control is a promising option to maintain acceptable levels of tick populations in cattle. Therefore, the present study evaluated the association of deltamethrin and the entomopathogenic fungus Metarhizium anisopliae against B. microplus larvae resistant to pyrethroid. The synthetic pyrethroid, deltamethrin, was used at concentrations of 0.39, 0.78, 1.56, 3.12 and 6.12 ppm, M. anisopliae was used at concentrations of 10(5), 10(6), 10(7) and 10(8) conidia ml(-1). Their associations were also evaluated in in vitro tests. The assays showed that the tick strain is resistant to deltamethrin, but high mortality rates were observed when deltamethrin was associated with the entomopathogen. The larvae's mortality rates ranged from 7 to 36.5% for the different concentrations of deltamethrin, however, for the different concentrations of M. anisopliae, the mortality rates ranged from 10 to 96.9%. Mortality rates were proportional to the concentrations used for both deltamethrin and the fungus. Predominantly, the association of pyrethroid and fungus resulted in higher larvae mortalility rates than those obtained with the respective non-associated concentrations. Thus, the present study indicates that this association can be used as a tool for integrated control of the tick B. microplus.     

First detection of Ixodes ricinus on beef cattle in Israel

This is the first report of the presence of Ixodes ricinus on beef cattle in Israel. Up to now, in the Middle East this tick was considered to be confined to Turkey and northern Iran. In the present study, tick samples collected from field-grazing beef cattle in western Galilee (northern Israel) were first examined morphologically for species-specific taxonomical features and then by molecular characterization. Ticks identified morphologically as I. ricinus were then examined by PCR with four different molecular markers: 12S rRNA, 16S rRNA, COX1 and cytochrome B. The PCR products were sequenced and compared with annotated I. ricinus sequences in GenBank? and the analyzed sequences from the collected samples shared 98–99% identity with reported I. ricinus sequences. In contrast, sequences from the collected ticks shared identity of 91% or less with annotated sequences from other Ixodes species. Multiple alignments and neighbor-joining analyses performed for each of the four markers reinforced the results obtained from pairwise alignments. These findings demonstrated for the first time the presence in Israel of the tick species I. ricinus – with results confirmed by a combination of morphological examination and molecular analyses.     

Long-term efficacy of a deltamethrin-impregnated collar for the control of the Australian paralysis tick, Ixodes holocyclus, on dogs

Objective To determine the duration of efficacy of a 4% deltamethrin‐impregnated collar for dogs (Scalibor® ProtectorBand, MSD Animal Health) against adult female paralysis ticks (Ixodes holocyclus). Procedures A controlled pen study was conducted. Dogs were artificially infested at 14‐day intervals with unfed adult female ticks for up to 140 days following application of the collar to the dogs. Efficacy was assessed by manually counting ticks on dogs at 24, 48 and 72 h after each infestation. Results Efficacy at the 72‐h count was 96% after the day 14 tick infestation. The 72‐h efficacy remained above 94% from the day 14 to the day 98 infestations, when efficacy was still 99.5%. Efficacy at 72 h was above 90% after the day 112 infestation and was still 93% at 72 h after the day 140 infestation. Conclusions The deltamethrin‐impregnated collar gave greater than 90% control of paralysis ticks for at least 14 weeks.     

An electron microscopic study of Cytoecetes phagocytophila infection in Ixodes ricinus

Tick-borne fever, caused by a rickettsia-like organism, Cytoecetes phagocytophila, is transmitted by the sheep tick Ixodes ricinus. An electron microscopic technique was developed to examine I ricinus for C phagocytophila infection. Infected and uninfected ticks were obtained from a laboratory maintained tick culture. All stages of I ricinus collected from one field site were examined; 44 per cent of nymphae and 32 per cent of adults were infected with C phagocytophila, but larvae were uninfected. This supports the previously held theory of transtadial, but not transovarial transmission of tick-borne fever.     

The dispersion of the Karoo paralysis tick, Ixodes rubicundus, within a naturally infested population of sheep in South Africa

The ratio of variance to mean (s2/means) of numbers of Ixodes rubicundus (males and females) per sheep was used as a measure of the dispersion pattern of this tick within a naturally infested population of sheep. Sheep were divided into two groups, one with previous contact with I. rubicundus and the other with no previous contact. Samples of 10 sheep from each group were searched for ticks on a weekly basis for 19 weeks during the winter of 1986. In each group, both male and female ticks had an s2/means ratio greater than 1 for the majority of observation periods indicating an aggregated dispersion pattern. The degree of aggregation was greater with increasing density of the ticks. The implications of these results are discussed both in relation to sampling procedures and potential control strategies.     

气相色谱法测定羊组织中溴氰菊酯残留

用气相色谱法对羊肌肉、肝脏、肾脏等组织中的溴氰菊酯残留进行检测.用石油醚、乙醚进行提取,硅胶柱净化,采用DB-5弹性石英毛细管柱(30 m×0.25 mm×0.25 μm)气相色谱法测定.溴氰菊酯标准曲线线性范围为25～1 000 ng/mL,相关系数为0.999 6,线性关系良好,在各组织中的回收率为84%～108%,适用于羊组织中溴氰菊酯残留的检测.